How is potassium dichromate prepared from sodium dichromate?

Step-by-step solution

Dichromates are generally prepared from chromate, which in turn are obtained by the fusion of chromite ore (FeCr 2 O 4 ) with sodium or potassium carbonate in free access of air. The yellow solution of sodium chromate is filtered and acidified with sulphuric acid to give a solution from which orange sodium dichromate, Na 2 Cr 2 O 7 . 2H 2 O can be crystallised. Sodium dichromate is more soluble than potassium dichromate. The latter is therefore, prepared by treating the solution of sodium dichromate with potassium